chore(paystack): Allow either v5 or v6 of guzzle to be used

Author: unicodeveloper

composer.json

@@ -14,7 +14,7 @@
     "php": ">=5.5.9",
     "illuminate/support": "5.2.*",
     "illuminate/container": "5.2.*",
-    "guzzlehttp/guzzle": "5.0|6.*"
+    "guzzlehttp/guzzle": "5.*|6.*"
    },
    "require-dev": {
         "phpunit/phpunit" : "4.*",